Control circuit for an adsorption or desorption system



Jan. 3, 1967 T. J. SLONE 3,295,172

CONTROL CIRCUIT FOR AN ADSORPTION OR DESORPTION SYSTEM 5 rs TEM S YsrsmFiled Oct. 20. 1965 I INVENTOR Tim/W95 .Z 54 we ATTORNEY United StatesPatent O 3,295,720 CONTROL CIRCUIT FOR AN ABSORPTION OR DESORPTIONSYSTEM Thomas J. Slone, Silver Spring, Md., assignor to Americaninstrument Co., Inc., Silver Spring, Md. Filed Oct. 20, 1965, Ser. No.498,943 8 Claims. (Cl. 222-3) This invention relates to fluid flowcontrol systems, and more particularly to means for controlling thevalves in a fluid adsorption or desorption system so as to automaticallyopen and close the valves in response to extreme variations in theaccumulation of fluid in a portion of the system.

A main object of the invention is to provide an improved control circuitfor use in fluid adsorption or desorption systems, the circuit acting tomonitor the system with which it is employed so a to maintain the fluidpressure therein between predetermined limits, the circuit beingrelatively simple in construction, being stable in operation, beingrelatively unaffected by switching transients, and being relativelyinsensitive to contact resistance effects.

A further object of the invention is to provide an improved monitoringcircuit for a fluid adsorption or desorption system wherein pressurefluctuations may occur in a portion of the system caused by changingcondi tions in the system, the circuit involving relatively inexpensivecomponents, being reliable in operation, being substantially immune totransients, and automatically setting itself to operate in the properdirection so that it cannot cause any unwanted valve operations.

A still further object of the invention is to provide an automatic fluidflow control system employing a mercury column as a pressure-sensitiveelement reacting to changes in pressure in a certain portion of a fluidadsorption or desorption system and coasting with spaced contacts tosignal abnormal pressure conditions in the system, the system includinga control circuit which responds to the fluctuations in height of themercury column to operate valves in the system in a manner to reversethe direction of fluid flow as required for normal adsorption ordesorption operation, the circuit being substantially unaffected bypower transients or interruptions, being relatively free of switchingtransients and being very stable in performance.

Further objects and advantages of the invention will become apparentfrom the following description and claims, and from the accompanyingdrawings, wherein:

FIGURE 1 is a schematic block diagram of a fluid adsorption systemprovided with an improved monitoring and stabilizing circuit constructedin accordance with the present invention.

FIGURE 2 is a schematic block diagram of a fluid desorption systememploying an improved control circuit according to the presentinvention.

Referring to the drawings, and more particularly to FIGURE 1, 11designates a system, for example, an apparatus for measuring porosity,or other equivalent apparatus, wherein doses of a suitable pressurizedgas, such as nitrogen from a supply source 12, are to be fed in a mannerto be adsorbed in the system and wherein it is necessary to maintain thegas pressure in a supply conduit 13 leading to the system betweenpredetermined limiting values for proper operation of the apparatus.

As shown in FIGURE 1, the pressurized nitrogen supply source 12 isconnected by a conduit 16 to the supply conduit 13 through suitablecontrol valve means, such as an electromagnetically operated valve 14provided with an operating solenoid or equivalent electrical actuatordesignated at 15. The supply conduit 13 is provided with a similar valve17, located between the systom 11 and the connnection to conduit 13, asshown, the valve 17 being provided with an operating solenoid orequivalent electrical actuating means designated at 18. The valves 14and 17 open responsive to the energization of their respective actuatingmeans 15 and 18.

esignated at 19 is a U-tube containing mercury 20 and having theupstanding vertical mercury column arm 21, the top of which isevacuated, the opposite arm 22 being connected to the supply conduit 13so that variations in gas pressure in the conduit 13 cause correspondingfluctuations in the height of the mercury column in arm 21. A pair ofvertically spaced contacts 23 and 24 in the upper portion of arm 21respectively represent the desired high and low mercury level limitscorresponding to the limiting high and low gas pressure values which canbe tolerated in conduit 13 to maintain proper dosage of nitrogen to thesystem 11.

Column arm 21 is provided with a bottom contact 25 which is in constantelectrical contact with the mercury 2t).

Energization of the valve actuators 15 and 18 is controlled by aconventional two-coil latching relay, designated generally at 26, whichmay be similar to Model KBl7DG, manufactured by Potter and Brumfield, adivision of American Machine and Foundry Co., Princeton, Indiana. Relay26 is provided with the upper coil 27, the lower coil 28, and one ormore poles 2%, each engageable either with an associated upper contact30 or an associated lower contact 31, depending upon which coil 27 or 28was last energized. FIGURE 1 illustrates the relay pole 29 in engagementwith its upper contact 30.

Pole 29 is connected by a wire 32 to the positive terminal of a suitablecurrent supply source, such as a 24 volt D.C. supply source. Thenegative terminal of said source is grounded, as by a wire 33.

One terminal of each of the valve actuators 15 and 13 is grounded, theother terminals thereof being connected respectively by wires 34 and 35to the relay contacts 3t) and 31. In the position of pole 29 shown,valve actuator 15 is energized, since Wire 34 is connected throughcontact 319 and pole 29 to the positive supply wire 32. This opens valve14 and allows pressurized I nitrogen to flow into supply conduit 13.When relay coil 28 becomes energized, pole 29 disengages from contact3t), deenergizing actuator 15 and closing valve 14, and engages contact31, energizing actuator 18 and opening system valve 17, thereby allowingthe nitrogen from conduit 13 to be admitted into the system 11.

Designated generally at 36 is a trigger circuit for selectivelyenergizing the relay coils 27 and 28 in accordance with the fluctuationsof the height of the column of mercury 20 in arm 21.

The doser trigger circut comprises a PNP transistor Q connected so as tocontrol relay coil 27 and an NPN transistor Q connected so as to controlrelay coil 28. Bottom contact 25 is connected by wires 37 and 38 to thepositive current supply wire 32. The base of transistor Q is connectedby a wire 39 through a Zener diode CR and a resistor R to ground. Zenerdiode CR is rated to conduct at approximately 14 volts, and may besimilar to General Electric Co. type Z4XL14. Resistor R has a value of2400 ohms. Contact 24 is connected by a wire 40 to wire 39. Wire 38 isconnected through a series of four diodes 41 to the emitter oftransistor Q One terminal of upper relay coil 27 is grounded and theother terminal thereof is connected by a wire 42 to the collector oftransistor Q -Upper contact 23 is connected by a wire 43 through aresistor R to the base of transistor Q Resistor R has a value of 240ohms. The base of transistor Q is connected to ground through a resistorR of 70 ohms. One terminal of lower relay coil 28 is connected topositive supply wire 32 and the other terminal thereof is connected by awire 44 to the collector of transistor Q The emitter of transistor Q isgrounded.

When the column of mercury 20 in arm 21 is below contact 24, transistorQ is conducting, so that wire 42 is connected through the diodes 41 andwire 38 to positive supply Wire 32. Relay coil 27 is energized, and pole29 engages contact 30, thus energizing valve actuator and causing valve14 to open. Nitrogen is admitted into conduit 13, causing the mercurycolumn to rise. When the mercury engages contact 24, the base oftransistor Q is connected to positive supply wire 32 through wire 40,mercury 20, and wires 37 and 38. This turns off transistor Qdeenergizing relay coil 27. However, pole 29 remains in engagement withcontact and valve actuator 15 remains energized, keeping valve 14 open.As the mercury in arm 21 continues to rise it engages upper contact 23,thereby connecting the base of transistor Q to positive supply wire 32through resistor R wire 43, mercury 20 and wires 37 and 38. This placessufficient bias on the base of transistor Q to cause said transistor toconduct, thereby connecting wire 44 to ground and cansing lower relaycoil 28 to become energized. This moves pole 29 away from contact 30 andinto engagement with lower contact 31, thereby deenergizing valveactuator 15 and energizing valve actuator 18. Valve 14 closes, cuttingoff the supply of nitrogen, and valve 17 opens, allowing the gas inconduit 13 to be admitted into the system 11. As the gas is adsorbed,the pressure in conduit 13 drops and the mercury 20 drops below contact23, turning off transistor Q and deenergizing relay coil 28. However,pole 29 remains in engagement with lower contact 31, keeping valve 17open until the mercury 20 drops below contact 24, thereby removing thepositive voltage from the base of transistor Q whereupon transistor Qagain conducts and energizes upper relay coil 27, moving pole 29 awayfrom contact 31 and into engagement with upper contact 30. Valve 14 isthus reopened to admit another dose of nitrogen into conduit 13.

It will be noted that neither relay coil 27 or 28 is energized when themercury level is between contacts 23 and 24, but the relay retains thesame state produced by the coil thereof last energized. The circuit istherefore such that it remembers during power transients orinterruptions in which direction the mercury column was travellingbefore the interruption and continues or resumes its travel in theproper direction when normal power is restored.

By placing the high and low contacts 23 and 24 in the base circuits ofthe transistors (to furnish power to the relay coils), a large amount ofcontact resistance (several hundred ohms in the worst case) can betolerated before reliable control is impaired. Electrodes 23 and 24 arepreferably made of platinum, and work well in the unsealed manometercolumn 21.

In FIGURE 2, the same trigger circuit 36 is employed except that itcontrols desorption from the system 11. The term desorption is definedin Chambers Technical ictionary, third edition, MacMillan Company, NewYork, revised 1958, as: The removal of a substance from the surface atwhich it is adsorbed. The word desorb is therefore accordingly definedherein as: To remove a substance from a surface at which it is adsorbed.A vacuum pump or other vacuum means is connected through conduit 16 andvalve 14 to the conduit 13. The ungrounded terminal of valve actuator 15is connected by a wire 34' to lower relay contact 31 land the ungroundedterminal of valve actuator 18 is connected by a wire 35' to the upperrelay contact 30. When the mercury 20 is below contact 24, actuator 18is energized and valve 17 is open, allowing gas to be desorbed from thesystem 11 into conduit 13. When the gas pressure in conduit 13 issufficient to raise the mercury 21 into contact with electrode 24, relaycoil 27 becomes deenergized, but valve actuator 18 remains energizeduntil the mercury rises sufficiently to engage upper electrode 23. Atthis point, transistor Q conducts, energizing lower relay coil 28,causing pole 29 to disengage from upper contact 30 and engage lowercontact 31. This closes system valve 17 and opens the vacuum valve 14,allowing the accumulated gas to be drawn out of conduit 13. Valve 14remains open when the mercury level drops below electrode 23, since pole29 continues to engage lower contact 31. As the mercury level dropsfurther and falls below electrode 24, transistor Q conducts and againenergizes relay coil 27, causing vacuum valve 14 to close and systemvalve 17 to reopen.

The valve control arrangement of FIGURE 2 provides the same advantagesabove mentioned in connection with the arrangement of FIGURE 1.

While certain specific embodiments of fluid flow control systems havebeen disclosed in the foregoing description, it will be understood thatvarious modifications within the spirit of the invention may occur tothose skilled in the art. Therefore it is intended that no limitationsbe placed onthe invention except as defined by the scope of the appendedclaims.

What is claimed is: I

1. A doser trigger control circuit fora fluid distributing assembly ofthe type comprising a main conduit connected to a system which adsorbsor desorbs gas and a branch conduit connected to said main conduit forsupplying gas to or releasing gas from said main conduit, said mainconduit being provided with a normally closed system valve locatedbetween said system and the branch conduit and said branch conduit beingprovided with a normally closed branch valve, first electrical actuatormeans operatively connected to said system valve, second electricalactuator means operatively connected to said branch valve, a mercurymanometer connected to said main conduit and having an upstanding armcontaining a column of mercury which rises and falls responsive toincreases and decreases of fluid pressure in said main conduit, atwo-coil latching relay comprising a first coil and a second coil, acontact pole, and respective stationary contacts engageable by said poleresponsive to the preceding energization of a corresponding one of saidcoils, circuit means to energize the first actuator means when the poleengages one of said stationary contacts, whereby to open said systemvalve while the branch valve remains closed, circuit means to energizethe second actuator means when. the pole engages the other of saidstationary contacts, whereby to open the branch valve and close thesystem valve, a pair of vertically spaced electrodes in said upstandingarm, means to energize one of said relay coils when the mercury dropsbelow the lower electrode, and means to energize the other relay coilwhen the mercury rises suificiently to engage the upper electrode.

2. A closer trigger control circuit for a fluid distributing assembly ofthe type comprising a main conduit connected to a system which adsorbsor desorbs gas and a branch conduit connected to said main conduit forsupplying gas to or releasing gas from said main conduit, said mainconduit being provided with a normally closed system valve locatedbetween said system and the branch conduit and said branch conduit beingprovided with a normally closed branch valve, first electrical actuatormeans operatively connected to said system valve, second electricalactuator means operatively connected to said branch valve, a mercurymanometer connected to said main conduit and having an upstanding armcontaining a column of mercury which rises and falls responsive toincreases and decreases of fluid pressure in said main conduit, atwo-coil latching relay, means to energize only the first actuator meansresponsive to the energization of one of the coils of the relay, wherebyto open said system valve while the branch valve remains closed, meansto energize only the second actuator means responsive to theenergization of the other coil of the relay, whereby to open the branchvalve and close the system valve, a pair of vertically spaced electrodesin said upstanding arm, means to energize only one of said relay coilswhen the mercury drops below the lower electrode, and means to energizeonly the other relay coil when the mercury rises sufficiently to engagethe upper electrode.

3. A doser trigger control circuit for a fluid distributing assembly 'ofthe type comprising a main conduit connected to a system which adsorbsor desorbs gas and a branch conduit connected to said main conduit forsupplying gas to or releasing gas from said main conduit, said mainconduit being provided with a normally closed system valve locatedbetween said system and the branch conduit and said branch conduit beingprovided with a normally closed branch valve, first electrical actuatormeans operatively connected to said system valve, second electricalactuator means operatively connected to said branch valve, a mercurymanometer connected to said main conduit and having an upstanding armcontaining a column of mercury which rises and falls responsive toincreases and decreases of fluid pressure in said main conduit, atwo-coil relay, means to energize only the first actuator meansresponsive to the energization of one of the coils of the relay, wherebyto open said system valve while the branch valve remains closed, meansto energize only the second actuator means responsive to theenergization of the other coil of said relay, whereby to open the branchvalve and close the system valve, means to energize only one of saidrelay coils when the mercury drops below a predetermined lower levellimit, and means to energize only the other relay coil when the mercuryrises to a predetermined upper level limit in said upstanding arm.

4. In a fluid distribution assembly, a system which adsorbs or desorbsgas, a main conduit connected to the system, a branch conduit connectedto said main conduit for supplying gas to or releasing gas from saidmain conduit, said main conduit being provided with an electricallyoperated normally closed system valve located between said system andthe branch conduit, said branch conduit being provided with anelectrically operated normally closed branch valve, a two-coil relay,means to energize the system valve responsive to the energization of oneof the relay coils, means to energize the branch valve responsive to theenergization of the other relay coil, means to energize only one of therelay coils when the gas pressure in the main conduit drops below apredetermined lower limit value, whereby to open one of said valveswhile the other valve remains closed, and means to energize only theother relay coil when the gas pressure in the main conduit reaches apredetermined upper limit value, whereby to open said other valve and toclose said one of the valves, said relay including means to maintaineach valve energized until the relay coil associated with the othervalve becomes energized.

5. In a fluid distribution assembly, a system which adsorbs or desorbsgas, a main conduit connected to the system, a branch conduit connectedto said main conduit for supplying gas to or releasing gas from saidmain conduit, said main conduit being provided with an electricallyoperated normally closed system valve located between said system andthe branch conduit, said branch conduit being provided with anelectrically operated normally closed branch valve, pressure-responsivemeans connected to said main conduit, a two-coil relay, means toenergize the system valve responsive to the energization of one of therelay coils, means to energize the branch valve responsive to theenergization of the other relay coil, first circuit means operativelycontrolled by said pressureresponsive means to energize only one of therelay coils when the gas pressure in the main conduit drops below apredetermined lower limit value, whereby to open one of said valveswhile the other valve remains closed, and second circuit meansoperatively controlled by said pressure-responsive means to energizeonly the other relay coil when the gas pressure in the main conduitreaches a predetermined upper limit value, whereby to open said othervalve and to close said one of the valves, said relay including means tomaintain each valve energized until the relay coil associated with theother valve becomes energized.

6. The assembly recited in claim 5, and wherein said first circuit meanscomprises a source of current, a first transistor, and means connectingsaid one relay coil.to said source through said first transistor, andwherein said second circuit means comprises a second transistor andmeans connecting the other relay coil to the source through said secondtransistor, and circuit means including said pressure-responsive meanscontrolling the bias voltages applied to said transistors.

7. The assembly recited in claim 5, wherein said pressure-responsivemeans comprises a mercury manometer tube provided with a bottomelectrode and vertically spaced upperand lower-pressure limitelectrodes, and wherein said first circuit means comprises a source ofcurrent, a first transistor, and means connecting said one relay coil tosaid source through said first transistor, and wherein said secondcircuit means comprises a second transistor and means connecting theother relay coil to the source through said second transistor, circuitmeans connecting the source to the control electrode of the firsttransistor through said bottom electrode and said lowerpressure limitelectrode, and circuit means connecting the source to the controlelectrode of the second transistor through said bottom electrode andsaid upper-pressure limit electrode.

8. The assembly recited in claim 7, and circuit means to render thefirst transistor conducting when the mercury level drops below the levelof the lower-pressure limit electrode, and circuit means to render thesecond transistor conducting when the mercury level rises to the levelof the upper-pressure limit electrode.

References Cited by the Examiner UNITED STATES PATENTS ROBERT B. REEVES,Primary Examiner.

N. L. STACK, Assistant Examiner.

4. IN A FLUID DISTRIBUTION ASSEMBLY, A SYSTEM WHICH ADSORBS OR DESORBSGAS, A MAIN CONDUIT CONNECTED TO THE SYSTEM, A BRANCH CONDUIT CONNECTEDTO SAID MAIN CONDUIT FOR SUPPLYING GAS TO OR RELEASING GAS FROM SAIDMAIN CONDUIT, SAID MAIN CONDUIT BEING PROVIDED WITH AN ELECTRICALLYOPERATED NORMALLY CLOSED SYSTEM VALVE LOCATED BETWEEN SAID SYSTEM ANDTHE BRANCH CONDUIT, SAID BRANCH CONDUIT BEING PROVIDED WITH ANELECTRICALLY OPERATED NORMALLY CLOSED BRANCH VALVE, A TWO-COIL RELAY,MEANS TO ENERGIZE THE SYSTEM VALVE RESPONSIVE TO THE ENERGIZATION OF ONEOF THE RELAY COILS, MEANS TO ENERGIZE THE BRANCH VALVE RESPONSIVE TO THEENERGIZATION OF THE OTHER RELAY COIL, MEANS TO ENERGIZE ONLY ONE OF THERELAY COILS WHEN THE GAS PRESSURE IN THE MAIN CONDUIT DROPS BELOW APREDETERMINED LOWER LIMIT VALUE, WHEREBY TO OPEN ONE OF SAID VALVESWHILE THE OTHER VALVE REMAINS CLOSED, AND MEANS TO ENERGIZE ONLY THEOTHER RELAY COIL WHEN THE GAS PRESSURE IN THE MAIN CONDUIT REACHES APREDETERMINED UPPER LIMIT VALUE, WHEREBY TO OPEN SAID OTHER VALVE AND TOCLOSE SAID ONE OF THE VALVES, SAID RELAY INCLUDING MEANS TO MAINTAINEACH VALVE ENERGIZED UNTIL THE RELAY COIL ASSOCIATED WITH THE OTHERVALVE BECOMES ENERGIZED.